Add Python 3.12 and limit MacOS tests.

[b-butler]

Description

Add Python 3.12 to CI and only test MacOS on oldest and newest Python/dependencies.

Motivation and Context

• Officially support newest Python.
• Reduce load on MacOS organizational runners.

Checklist:

• I am familiar with the Contributing Guidelines.
• I agree with the terms of the Contributor Agreement.
• My name is on the list of contributors.
• The changes introduced by this pull request are covered by existing or newly introduced tests.
• The package documentation and framework documentation in signac-docs are up to date with these changes.
• I have updated the changelog and added any related issue and pull request numbers for future reference.

[csadorf]

LGTM, but tests are failing.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (8477337) 69.11% compared to head (0252b37) 69.11%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #788   +/-   ##
=======================================
  Coverage   69.11%   69.11%           
=======================================
  Files          45       45           
  Lines        4348     4348           
  Branches     1055     1055           
=======================================
  Hits         3005     3005           
  Misses       1137     1137           
  Partials      206      206           

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